In many applications, it is desired to detect non-visible features and produce visible images of the non-visible features—typically onto surfaces that obscure the non-visible features. This can be useful in instances in which a viewer needs simultaneously to see a non-visible feature and the visible image of the non-visible feature. For example, it is useful to locate subcutaneous features, such as veins, tumors, nerves, bones, foreign objects when investigating a body part. Vein viewing systems have been developed to allow medical personnel to locate veins to administer injections and intravenous delivery of drugs and fluids. Likewise, the ability to view internal structures of objects such as vehicles, walls, or buildings without having to touch or open the objects is useful.
It is also useful in camouflaging or veiling visible features or objects. For example, wherein an object stands in front of a background and conceals a portion of the background, the object can be obscured or hidden by producing an image of the concealed portion of the background to the corresponding surface portion of the object. As a consequence, the produced image on the object's surface and the exposed portion of the background form a “continuous” background—resulting in a visual effect of object-hiding.